Stents are frequently used to enlarge, dilate, or maintain the patency of narrowed body lumens. Non-expandable stents are typically made from plastics and contain a lumen extending throughout.
Implantation of biliary stent structures provides treatment for various conditions, such as obstructive jaundice. Biliary stenting treatment approaches can be used to provide short-term treatment of conditions such as biliary fistulae or giant common duct stones. Biliary stents may be implanted to treat chronic conditions such as postoperative biliary stricture, primary sclerosing cholangitis and chronic pancreatitis.
A biliary stent can be made in the form of a polymer tube that can be advanced on a delivery catheter through an endoscope and into the bile duct where it is deployed. The tubular stent is selected to be sufficiently strong to resist collapse to maintain an open lumen through which digestive liquids can flow into the digestive tract. Among the desirable features of such a stent is that it be longitudinally flexible to be advanced along a path that may include sharp bends. The stent also should maintain its intended position within the bile duct without migrating from that position.
As bodily fluid travels through the lumen of the stent, cumulative matter within the bodily fluid adheres to the inner surface of the stent. Cumulative matter is material traversing the stent that if undisturbed, would otherwise accumulate on the passageway surfaces to reduce the diameter of the flow path and could eventually clog the stent. Cumulative matter includes, but is not limited to biofilm, bacterial growth, and sludge deposition. Thus, cumulative matter can prevent further bodily fluid from passing therethrough. A biliary stent can become occluded within a bile duct, as cumulative material, such as an encrustation of amorphous biological material and bacteria (“sludge”), accumulates on the surface of the stent gradually obstructing the lumen of the stent. Biliary sludge is an amorphous substance often containing crystals of calcium bilirubinate and calcium palimitate, along with significant quantities of various proteins and bacteria. Sludge can deposit rapidly upon implantation in the presence of bacteria. For example, bacteria can adhere to plastic stent surfaces through pili or through production of a mucopolysaccharide coating. Bacterial adhesion to the surface of a stent lumen surface can lead to occlusion of the stent lumen as the bacteria multiply within a glycocalyx matrix of the sludge to form a biofilm over the sludge within the lumen of an implanted drainage stent. The biofilm can provide a physical barrier protecting encased bacteria from antibiotics. With time, an implanted biliary stent lumen can become blocked, thereby restricting or blocking bile flow through the biliary stent. As a result, a patient can develop symptoms of recurrent biliary obstruction due to restricted or blocked bile flow through an implanted biliary stent, which can be complicated by cholangitis and sepsis.
Often, such conditions are treated by antibiotics and/or endoscopic replacement of an obstructed biliary stent. Typically, biliary stents need replacing every three months. Replacement procedures cause medical risk and financial strain to the patient.
There exists a need in the art for an implantable medical device that prevents or reduces the biofilm and sludge deposition process inside the lumen of implantable drainage stents, such as biliary stents. There is a need for a non-expandable stent that resists clogging, for example by mechanical means.